Prior to the present invention, moisture curable epoxy compositions were provided which contained dicarbonyl chelates as curing agents, as shown by Cella, U.S. Pat. No. 4,116,886, assigned to the same assignee as the present invention. As taught by Cella certain moisture sensitive dicarbonyl chelates of main row elements of Group IIIa-Va, were capable of effecting the moisture cure of epoxy resins to provide sealants, coating compounds, glues and encapsulants. As shown in the above referenced copending application of James V. Crivello, Ser. No. 949,642, certain hexafluoro metalloid phosphonium salts, such as triphenylphenacylphosphonium hexafluorophosphate and hexafluoroarsenate, can be used as photoinitiators for epoxy coating compositions resulting in the production of tack-free films in a minute or less when exposed to ultra violet light. These UV curable compositions are also shown by Crivello U.S. Pat. No. 4,069,055 also assigned to the same assignee as the present invention.
It has now been discovered that certain aryloxy phosphonium salts of the formula, EQU [(RO).sub.n (R.sup.1).sub.4-n P].sup.+ [MQ.sub.d ].sup.- ( 1)
have been found useful as curing agents for epoxy resins when utilized in effective amounts to provide moisture curable cationically polymerizable coating compositions, where R and R.sup.1 are monovalent aryl radicals selected from C.sub.(6-13) hydrocarbon radicals and radicals of the formula ##STR1## where X is selected from C.sub.(1-8) alkoxy, nitrile, acyloxy, halogen and nitro, Y is selected from C.sub.(1-8) alkyl and X radicals, M is selected from B, As, Sb and P, O is a halogen radical, a is whole number equal to 0 to 4 exclusive, d is an integer equal to 4-6 inclusive, and n is an integer equal to 1 to 4 inclusive.